There is a demand for a heat-ray shielding film with a heat-ray shielding capability (heat-ray shielding function) that can reduce a cooling load, a person's sensation of heat, adverse effects on plants, etc., which is for blocking a part of incoming solar energy, with regard to applications such as window materials for automobiles, buildings, etc., and films for vinyl houses, etc.; and various studies have been made.
A case has been reported such that, when a heat-ray shielding film is used, for example, as a window material, the heat-ray shielding film is disposed between a plurality of sheets of glass facing each other as an intermediate layer (interlayer) to form a laminated glass.
As an example in which a laminated glass is formed, Patent Document 1 discloses a laminated glass in which a flexible resin layer is formed, which includes, between a glass pair, a heat ray-shielding metal oxide that is one of tin oxide or indium oxide with a particle size of less than or equal to 0.1 μm.
Further, Patent Document 2 discloses a laminated glass provided with an intermediate film layer obtained by dispersing, between at least two transparent glass plates, functional ultrafine particles, such as one of a metal, an oxide, a nitride, a sulfide, and a Sb or F-doped material of Sn, Ti, Si, Zn, Zr, Fe, Al, Cr, Co, Ce, In, Ni, Ag, Cu, Pt, Mn, Ta, W, V, or Mo, or a composite obtained by selecting two or more of them.
Further, Patent Document 3 discloses a vehicle window glass obtained by forming, between transparent plates, a mixed layer of ultrafine particles with an average particle diameter of less than or equal to 0.1 μm and a glass component. As the ultrafine particles, a metal oxide of TiO2, ZrO2, SnO2, In2O3, etc., and a mixture thereof are exemplified; and, as the glass component, organic silicon or an organic silicon compound is exemplified.
Furthermore, Patent Document 4 discloses a laminated glass such that a laminated interlayer including three layers is formed between at least two transparent glass plates, and functional ultrafine particles, such as one of a metal, an oxide, a nitride, a sulfide, and a Sb or F-doped material of Sn, Ti, Si, Zn, Zr, Fe, Al, Cr, Co, In, Ni, Ag, Cu, Pt, Mn, Ta, W, V, or Mo, or a composite obtained by selecting two or more of them, are dispersed in the second layer of the interlayer.
However, a problem is that, when a high level of visible light transmittance is required, a heat-ray shielding property of each of the laminated glasses disclosed in Patent Document 1 through Patent Document 4 is not sufficient.
Accordingly, the applicant of the present invention has disclosed, in Patent Document 5, a solar radiation shielding laminated glass such that an intermediate layer provided with a solar radiation shielding function is disposed between two glass plates, and the intermediate layer is formed of: an additive solution, which is obtained by dispersing hexaboride fine particles in a plasticizer (or an additive solution obtained by dispersing hexaboride fine particles and ITO fine particles and/or ATO fine particles in a plasticizer); and an interlayer formed of a vinyl-based resin.
Further, Patent Document 5 also discloses a solar radiation shielding laminated glass formed of: a solar radiation shielding film obtained by forming an intermediate layer provided with a solar radiation shielding function on a surface located at an inner side of at least one of two glass plates while disposing the intermediate layer between the two glass plates, and by applying, to the intermediate layer, a coating liquid including hexaboride fine particles as the solar radiation shielding component (or a coating solution including, as the solar radiation shielding component, hexaboride fine particles and at least one of ITO fine particles and ATO fine particles); and an interlayer disposed between the two glass plates and including a vinyl-based resin.
In a film in which hexaboride fine particles used in the solar radiation shielding laminated glass disclosed in Patent Document 5 are sufficiently dispersed finely and uniformly, the transmittance has a maximum value in a wavelength range from 400 nm to 700 nm, and has a minimum value in a wavelength range from 700 nm to 1800 nm. As a result, according to the solar radiation shielding laminated glass disclosed in Patent Document 5, even if the visible light transmittance is adjusted to be 77% or 78%, the solar radiation transmittance is approximately from 50% to 60%, and the performance is greatly improved compared to conventional laminated glasses disclosed in Patent Documents 1 through 4.
Furthermore, the applicant of the present invention discloses, in Patent Document 6, a solar radiation shielding laminated structure that is obtained by using, as fine particles provided with a solar radiation shielding function, tungsten oxide fine particles, and/or composite tungsten oxide fine particles, and by disposing, between two laminated plates selected from glass plates, etc., an intermediate layer obtained by dispersing, in a synthetic resin, such as a vinyl-based resin, fine particles provided with a solar radiation shielding function.
For the solar radiation shielding structure disclosed in Patent Document 6, there is a case in which the solar radiation transmittance is 35.7% when the visible light transmittance is 70.7%, and the performance is further improved compared to the conventional laminated glass described in Patent Documents 1 through 5.